Gas tube voltage regulator



March 27, E. O JOHNSON GAS TUBE VOLTAGE REGULATOR Filed Jan. 2, 1951 l N V E N TO R EJ211321] a cfofizzson ATTORNEY United States Patent'O GAS TUBE VOLTAGE REGULATOR Edward Oscar Johnson, Princeton, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application January 2, 1951, Serial No. 203,949

8 Claims. (Cl. 323-22) This invention relates to improvements in electrical power supply systems, and particularly to power supply systems utilizing gas filled electron tubes.

In electrical apparatus requiring unidirectional operating voltage, it is customary to provide a so-called power supply-system for converting alternating voltage from a commercial outlet to unidirectional voltage.

Frequently, the operating characteristics of a given electrical apparatus require that the unidirectional operating voltage supplied thereto be kept relatively constant, or regulated, notwithstanding changes in the source voltage or in the load on the power supply. Regulated power supplies frequently include a grid-controlled vacuum tube connected between the power supply rectifier and the load, withthe impedance of the tube being varied in accordance with the voltage furnished to the load.

Regulated power supplies of this type have definite disadvantages. Since vacuum tubes inherently are relatively high impedance devices, they cannot pass large amounts of current to the load without substantial voltage losses. Even for a load requiring only, say, 100 milliamperes of current, it is not unusual to find as many as four large triode tubes connected in parallel in a regulating system.

Furthermore, a grid-controlled vacuum tube has characteristics that make it unsuitable for use as a rectifier. Therefore, conventional regulated power supply systems ordinarily have separate rectifier and regulating tubes.

All of the above mentioned deficiencies of prior art regulated power supply systems add to the complexity, cost, size and weight thereof.

It is a general object of the present invention to provide a power supply system having relatively high current handling capability, good regulating characteristics, and unusual operating efiiciency.

A further object of the invention is to provide a system for supplying regulated unidirectional voltage to a load from a variable voltage source with a minimum of voltage loss.

Another object of the invention is to provide a power supply system wherein the functions of alternating voltage rectification and unidirectional voltage regulation are accomplished simultaneously.

In accordance with the invention, the foregoing and other related objects and advantages are obtained in a system utilizing a gaseous electron tube either as a variable impedance element or as a combined variable impedance element and rectifier. The gaseous electron tube utilized in accordance with the invention is of the type wherein separate potentials are used to provide the ionization needed for space charge neutralization and to provide the field needed for drawing current through the ionized gas. As will be pointed out more fully hereinafter, a system of this type can handle unusually large amounts of current and with very low voltage loss.

A more complete understanding of the invention can be had by reference to the following descriptions of illus- 2,740,089 Patented Mar. 27, 1956 ICC trative embodiments thereof, when considered in connection with the accompanying drawing, wherein:

Fig. 1 is a schematic diagram of a power supply system having a regulator embodying the present invention,

Fig. 2 is a sectional view of a gas filled electron tube such as may be used in the circuit of Fig. 1,

Fig. 3 illustrates a combined regulator and rectifier arranged in accordance with the invention, and

Fig. 4 illustrates a modified arrangement of a regulator embodying the principles of the invention.

Referring to the drawing, there is shown in Fig. 1 a power supply system having a regulator arranged in accordance with the present invention. The power supply of Fig. 1 includes a rectifying network 10 for converting alternating voltage, applied to the input terminals 12 thereof, into unidirectional voltage at a second pair of terminals 14a, 14b. The primary winding 16 of a transformer 18 is connected to the terminals 12, and a rectifier tube 20 is connected in series with a storage capacitor 22 across the secondary winding 24 of the transformer 18.

The rectifying network 10 is conventional in form. When alternating voltage is applied to the terminals 12, the rectifier 20 will conduct current on alternate half cycles, developing a unidirectional voltage of polarity as indicated across the capacitor 22. If desired, a filter choke 23 can be connected between the rectifier tube 20 and the positive output terminal 14a of the rectifying network.

If a load device were to be connected across the terminals 14a, 14b, it is possible that the voltage at these terminals might vary, due either to a change in the input voltage or to a change in the load. In order to compensate for such changes in accordance with the invention, a. gaseous electron tube 26 has its anode 28 connected to the positiveterminal 14a, and its principal cathode 30 connected to the output terminal 32a. Thus, the space path between the electrodes 28, 30 of the tube 26 is in series between the terminals 14a and 32a.

The gas tube 26 of Fig. i also is provided with an auxiliary cathode 34 from which current can flow either to the main cathode 30, or to the anode 28, or both. This current from the auxiliary cathode 34 is relied on to ionize the gas in the tube 26, and will be referred to hereinafter as the ionizing current. The ionizing current circuit is completed by connecting the auxiliary cathode 34 to the negative terminal 14b through a current limiting resistor 36.

The structural details of a typical tube such as the tube 26 are given hereinafter. A tube of this type is described more fully and claimed in the copending application of the present inventor, Serial No. 185,745, filed September 20, 1950, and assigned to the assignee of the present invention.

In the embodiment of the invention presently being described, the voltage supplied to the output terminal 32a from the positive terminal 14a of the voltage source 10 is regulated by varying the impedance (and, hence, the voltage drop) between the anode 28 and the main cathode 30 in the tube 26. This impedance can be regulated by applying a suitable control voltage to a control electrode 38 disposed between the anode 28 and the main cathode 30. One suitable source of such control voltage may comprise a potentiometer 40 connected between the output terminals 32a, 32b, and having a movable tap 42 which is connected to the control electrode 38 in the tube 26.

As is explained in the above-mentioned copending application, if the function of ionizing the gas in a gas filled electron tube is separated from the function of passing work circuit current between the main tube electrodes, it becomes possible to control the work circuit corresponding change in the work circuit current.

means of the control electrode 38.

Consider, for example, the'tube shown in cross section in Fig. 2. In Fig. 2, .a gas tighttenvelope 2:6 is provided with a cathodelsti. A U-shaped control electrodeor grid 38 and a U-shaped anode 2.8 partially surround the cathode 3G. The grid 38 comprises a plurality .of parallel wires .39 which are supported .in spaced relation. The anode 28 may be a sheet metalelement. Y

Opposite the open ends of .the grid .33 and the anode 28 there is mounted a cylindrical focusing electrode 23 provided with an elongated slot 25 facing the-open ends of the grid and anode structures. An auxiliary cathode 34 is mounted coaxially within the focusing, electrodej23.

A tube having .astructure .such as that shown in Fig. 2 can be operated as follows: i

. If .a voltage greater .than that required to ionizc gas in the tube 26 is applied between the auxiliary cathode 34 and the anode 28, a current will:fiow which will ionize the gas in the tube. As a result, a highly conductive mixture .or plasma of ions and electrons will be created within the tube envelope. The focusing electrode 23- is effective to concentrate the ionizing current, making it possible to obtain high plasma densities with tvery small amounts of current or power. With the tube gas ionized to create plasma in the mannerjust described, it becomes possible to pass a relatively high current between the main cathode and the main anode with a voltagedrop which may be of the order of 0.1 volt :or less. Furthermore, it also becomes possible to control this .main cathode-anode current by means of a control electrode disposed in the space path as shown.

With a tube of this type connected in 'a power supply system in the manner shown inFig. 1, certain important advantages can be obtained. First, as compared with a voltage regulating system wherein a conventional vacuum tube is utilized as a variable impedance element, .the voltage loss across the regulatory impedance will be very small. Furthermore, currents far in excess of those'which can be passed through a conventional vacuum tube will flow readily through, the conducting plasma .in the .gas tube, so that the current handling capabilities of the power supply system need not be limited by the inclusion of the regulator.

The system shownin Fig. l will operate in the following manner:

Assume that the voltage between the terminals 14a, 14btends to increase. This, in turn, will cause an increase in the voltage across the potentiometer 49, as measured at the main cathode of the gas tube 26. The voltage also will increase at the control electrode 38. However, since the voltage at the main cathode 30 will increase more than the control electrode voltage, the net eflect will he to make the control electrode 38 more negative with respect to the cathode 30. As a result, there will be an increase in the effective impedance between "the main cathode 3.0 and the anode '28, accompanied by an increase in the voltage dropbetween these electrodes 28, 30. This increase in voltage drop "will "tend to ofiset the original voltage change at the terminals 14a, 514]), and will tend to maintain :thevoltage between the output terminals 32a, 32b essentially constant.

It has been found 'thatchanges in the ionizing current in a tube of the type-shown in Figs. 1 and '2 will cause a In the case of the regulating arrangement-shownin Fig. '1, this change will be opposed to the desired regulatory action. That is, if the voltage between the auxiliary cathode 34 and the main electrodes 28, 30 were to increase, as in the example just given, a greater amount of ionizing current would flow, reducing the effective impedance between the anode 28 and the main cathode 30. This would tend to offset the regulatory .efiect .of the previously described change in control electrode voltage. If, in a given case, the effect of ionizing current changes cannot be tolerated, the arrangement shown in Fig. 3 can be adopted, wherein two expedients are shown for improvin the regulating action. Fig. 3 also illustrates a further important feature of the invention; namely, the combination of rectifying and regulatory action.

In the system shown in Fig. 3, the rectifying network it) of Fig. 1 has been eliminated. The tube anode 28 is connected directly to one terminal 24a of the transformer secondary winding 2 while the main cathode '30 is connected to the other secondary winding terminal .247; through the capacitor 22. Thus, the work circuitof .the gas tube 26 will supply rectified current to charge the capacitor 22.

The voltage across the capacitor 22 in Fig. 3 will be regulated by a control voltage applied to the control electrode 38 from an amplifying circuit. This amplifying circuit includes a resistor 44- connected in series with a conventional amplifier 45 across the capacitor 22.- A control voltage for the amplifier tube will be obtained from a potentiometer 4b which is connected in series with a conventional gas regulator tube 48 across the capacitor 22. The auxiliary cathode 34 of the ;gas tube 26 is connected through a current limiting resistor 36 to the junction of the regulator 43 and the potentiometer "40.

The regulatory action of the tube 26 in the circuit of Fig. v3 will be superior to that obtained with the system shown in Fig. l for two reasons. First, the regulator tube 48 will help to maintain substantially constant voltage .and, hence, substantially constant ionizing current between the auxiliary cathode 34 and the main electrodes 28, 39. This will tend to prevent the adverse effect of ionizing current changes previously referred to. Second, an amplified control voltage will be applied to the-control electrode 38.. This amplified control voltage will aid in oflsetting any adverse effect due to changes in the ionizing current.

Suppose, for example, that the voltage at the secondary Winding terminals 24a, 24]) increases. The voltage across the potentiometer 4% also will increase, causingthe amp'li fier tube 4-6 to draw more current. This will increase the voltage drop across the resistor 44, making the gas tube control electrode 38 more negative with respect to the main cathode 3t Thereupon, the efiective impedance between the gas tube anode 28 and the main cathode 30 will increase, offsetting the effect of the original voltage increase. a

.The circuits thus far described will provide regulatory compensation for voltage changes of several volts, and with a voltage loss in the regulator tube of no more than, say, 0.1 volt at the lowest source voltage. Also, currents of as much as one ampere can be handled readily in systems of the type described. However, the voltage between the gas tube anode 28 and the main cathode 30 should not exceed the ionizing potential of thetube gas. If this ionizing potential is exceeded, then an ionizing discharge may occur between the main cathode andthe anode, and grid control of the work circuit current will belost. If it is anticipated that the voltage may-change by an amount greater than the ionizing potential of the tube gas, the main electrodes of two or more gas tubes can be connected in series between the voltage'sourceand the load to insure that the voltage between the maintube electrodes of any one of the tubes will not exceed-the ionizing potential of the gas.

Such an arrangement is shown in 'Fig. 4, wherein the anode 28 of a first gaseous electron tube '26'is connected to an input terminal Tl, corresponding either to the ter minal 14a of Fig. 1 or to the terminal 24a :of Fig. 3. The cathode 30 of this first tube 26 is connected :to :the anode 50 of a second gas discharge tube 52. The weathode 54 of the .second tube 52 is connected .tothe output terminal 32a, and the control electrodes .38, .56 :of tubes '26, 52 are connected to adjustable taps 442,413 on a potentiometer an. Theauxiliary cathodes .34, 58 pfzthe gas tubes 26, 52 are connected through current limiting resistors 36, 60 to the junction between a regulator tube 48 and a resistor 62 which are in series across the potentiometer 40. Although not shown, an amplifier such as the amplifier 46 of Fig. 3 can be used in the circuit of Fig. 4.

In the circuit of Fig. 4, the regulating action of each of the tubes 26, 52 will be substantially the same as has already been described in connection with Figs. 1 and 3. The principal difference is in the fact that the voltage drop between the input terminal T1 and the output terminal 32a will be divided substantially equally between the two tubes 26, 50, making it possible to have a wider range of output voltage regulation but without adversely afiecting the gas tube operation.

From the foregoing, it will be apparent that the present invention provides a regulating arrangement for power supply systems characterized by low voltage losses, high current handling capabilities, and excellent control char acteristics.

What is claimed is:

1. In a system for converting alternating voltage to regulated unidirectional voltage wherein a gas tube having a plurality of electrodes is used as a variable resistance, an alternating voltage source, an impedance, a circuit connecting said impedance to said voltage source through the space path between a first pair of said electrodes, a control electrode between said first pair of said electrodes, a second circuit connecting said voltage source in series with the space path between a second pair of said electrodes, and a feedback circuit connected between said impedance and said control electrode to supply continuously between said control electrode and one of said first pair of said electrodes a voltage proportional to the voltage across said impedance, one of said electrodes being common to said first and second pairs of said electrodes.

2. In a voltage regulator system wherein a gas tube having a plurality of electrodes is used as a variable impedance, a voltage source, a load device, a circuit connecting said load device to said voltage source through the space path between a first pair of said electrodes, at second circuit connecting said voltage source between a second pair of said electrodes to generate a conductive ion-electron plasma in said tube in the area between said first pair of said electrodes, and means to control the voltage drop between said first pair of said electrodes continuously as a function of the voltage across said load device, said means including a voltage-feedback circuit connecting one of said first pair of said electrodes to another of said tube electrodes, one of said electrodes being common to said first and said second pairs of said electrodes.

3. In a system for supplying regulated unidirectional voltage wherein a gas tube having a plurality of electrodes is used as a variable resistance, a voltage source, an impedance, a circuit connecting said impedance to said voltage source through the space path between a. first pair of said electrodes, a control electrode between said first pair of said electrodes, a second circuit connecting said voltage source across the space path between a secand pair of said electrodes, and a feed-back circuit connected between said impedance and said control electrode to supply continuously between said control electrode and one of said first pair of said electrodes a voltage proportional to the voltage across said impedance, one of said electrodes being common to said first and said second pairs of said electrodes.

4. In a system for supplying regulated unidirectional voltage wherein a gas tube having a plurality of electrodes is used as a variable resistance, a pair of input terminals, a pair of output terminals, a circuit connecting one of said input terminals to one of said output terminals through the space path between a first pair of said electrodes, a connection between the other of said input and output terminals, a second circuit connecting said input terminals through the space bath between a second pair of said electrodes, and a feedback circuit connected between said one output terminal and said control electrode to supply continuously between said control electrode and one of said first pair of said electrodes a voltage proportional to the voltage across said output terminals, one of said electrodes being common to said first and said second pairs of said electrodes.

5. In a system for supplying regulated unidirectional voltage wherein a gaseous electron tube having a plurality of electrodes including an anode, a main cathode, and an auxiliary cathode is used as a variable resistance, a pair of input terminals, a pair of output terminals, a circuit connecting one of said input terminals to one of said output terminals through the space path between said anode and said main cathode, a connection between the other of said input and output terminals, means connecting said one output terminal to one of said electrodes to control the voltage between said one electrode and said main cathode continuously as a function of the voltage between said output terminals, and means connecting said main and auxiliary cathodes to maintain substantially constant voltage between said main and auxiliary cathodes.

6. A system as defined in claim 5 wherein said last named means comprises a gas regulator tube and a resistor connected in series between said output electrodes.

7. A system as defined in claim 5 wherein said first named means comprises a potentiometer connected in circuit between said output terminals, and a grid-controlled amplifier connecting said potentiometer to said one electrode.

8. In a voltage regulator system wherein a gas tube having a plurality of electrodes is used as a variable resistance, a voltage source, a load device, a circuit connecting said load device to said voltage source through the space path between a first pair of said electrodes, at second circuit connecting said voltage source between a second pair of said electrodes to generate a conductive ion-electron plasma in said tube in the area between said first pair of said electrodes, and means to control the voltage drop between said first pair of said electrodes continuously as a function of the voltage across said load device, said means including a voltage-feedback circuit connecting one of said first pair of said electrodes to said second circuit, one of said electrodes being common to said first and said second pairs of said electrodes.

References Cited in the file of this patent UNITED STATES PATENTS 2,428,048 Stutsman Sept. 30, 1947 2,435,961 Gibbons et al. Feb. 17, 1948 2,438,417 Russel Mar. 23, 1948 2,438,831 Sziklai Mar. 30, 1948 2,456,638 Kenyon Dec. 21, 1948 

